First Law: Energy cannot be created or destroyed and is transformed to another form. The total amount of energy stays constant, constantly changing form.
Second law: The transformation of energy from one state to another is never 100% efficient, some is always lost to another state, in most cases it is lost to heat.
Forms of Energy
Kinetic Energy
This type of energy refers to motion; any object that moves possesses kinetic energy.
Radiant energy comes under the kinetic heading; it is electromagnetic energy, which travels in waves. The length of the wave varies massively, from one end of the scale to the other; these waves also vary greatly in the level of energy they provide.
The sun provides a range of these waves; they are listed below in order of wavelength, starting with the shortest. Shorter wavelengths provide higher amounts of energy than the longer waves and are potentially dangerous because of their high amounts of energy.
- Gamma rays
- X-rays
- Ultraviolet rays
- Visible light
- Infra-red
- Microwaves
- Radio waves
Thermal energy is another form of kinetic energy, which relates to heat, heat is present where ever molecules and atoms vibrate or move about. The level of energy depends on the amount of movement going on inside the object or body, (higher temperatures contain more energy than lower ones).
Thermal energy can be transferred from one body to another in three ways, thermal conduction, convection and radiation. Heat is the result of many energy conversions and can be got from light, electrical, mechanical, chemical, nuclear and sound. For this reason heat is usually the cause for the second rule of thermodynamics.
Potential Energy
This types of energy relates to any object that has stored energy, this stored energy has the potential to change other objects; it is waiting to become kinetic.
Gravitational energy comes from an object that has a position or place; it is the effects of a gravitational force pulling on the object. When an object is raised its gravitational potential energy is increased, it is increased to an amount equal to the force used to lift it. The object will hold or store this energy until it is released and can fall to the ground. At this point the energy is converted into kinetic energy and when it hits the floor the energy is transformed to heat and sound. Gravitational potential energy is relative to its distance from the ground and mass.
This type of energy is what holds the solar system together; the gravitational force of the sun keeps the planets in its orbit.
Chemical energy is energy that is stored in an object due to its arrangement of atoms and molecules, the energy comes from the chemical bonds that hold the atoms and molecules together. Chemical energy is transformed into many other forms by chemical reactions be they natural or man-made.
- Petrol – Burnt to release energy (mainly heat)
- Food – Digested to release energy
- Plants – photosynthesis is a natural chemical reaction resulting from plant exposure to solar energy.
Earths Atmosphere
The atmosphere is the general name given to the layers of gas that envelop the earth. The atmosphere exists because of events that have happened in space and on the planet for billions of years and are still undergoing change with the aid of life on earth. Different amounts of gases are being consumed and emitted continually; the changes normally occur slowly giving the atmosphere time to stabilise but sometimes sudden large amounts of particular gasses are released, unbalancing the composition of the atmosphere.
The gases remain in the atmosphere rather than disappearing into space because they are attracted to the gravitational pull of the Earth, different gases have different weights and so the gas composition can be divided into two sections; homosphere, where the composition is generally mixed, this extends to about 80km vertically from the surface and the heterosphere which consists mainly of the lighter elements of helium and hydrogen above.
Atmosphere can also be divided into layer according to the temperature and pressure variations that occur throughout the atmosphere.
Troposphere
This is the layer closest to the surface and is heated from the surface as well as the above atmospheric layer. Temperature decreases with height in this layer, as the layer above increases with height this makes troposphere well mixed and thus quite turbulent. The turbulence means that this layer experiences nearly all the weather on the planet and is regarded as the “zone of weather”.
The troposphere extends to approximately 11-16km above the earths surface depending on where it is geographically. For example the troposphere extends higher in the tropics than it does over the poles, the higher temperatures from the surface create more turbulent mixing; pushing the boundary of the layer higher.
The boundary between the troposphere and the next layer is called the tropopause, this is the area where the temperature stabilises and remains constant with increased height. When the temperature begins to change with height you enter into the next layer.
The pressure within the troposphere decreases with height this is because pressure is the weight and force of the atmosphere upon the earth, so as the height rises the mass of atmosphere is reduced and thus the pressure.
Stratosphere
This layer lies above the tropopause and reaches heights of approximately 50km. This is a stable layer of atmosphere with little mixing and because of this pollutants that enter can reside in the stratosphere for many years.
Temperature increases with height in this layer this is because of the layer of ozone that is present, the ozone absorbs ultraviolet radiation emitted from the sun and when this happens heat is released warming the layer. The reaction occurs at the higher level of the stratosphere making the lower heights cooler because there is less UV radiation to absorb.
The absorption of UV rays in the ozone helps to protect the surface from harm; UV in large concentrations is very damaging to many forms of life. The pressure throughout this layer again reduces with height.
The stratopause is the area between the stratosphere and the layer above, where temperature remains constant with height before going into another stage of change.
99.9% of the atmosphere is contained within these two layers, which means that this is where the pressure is most exerted. Above these layers the atmosphere is filled with lighter particles that exert a minute force on the earths surface.
Gaseous composition of the lower atmosphere
- Nitrogen 78.1%
- Oxygen 20.9%
- Argon 0.9%
- Carbon dioxide, methane, rare (inert) gases 0.1%
The composition varies from place to place due to the presence of water vapour and aerosols.
Mesosphere
The mesosphere lies above the stratopause and extends to an altitude of approximately 85km. Temperature decreases with height in this layer, this is because there is no ozone present to absorb UV radiation and heat the layer. The lowest temperatures are experienced in the mesosphere, with temp dropping to a low of approx -100 degrees Celsius /173 degrees Kelvin.
It is in this layer that most meteors that have entered the atmosphere are burnt up, we can see this in what is commonly know as shooting stars. There is still a small trace of moisture at this height and noctilucent clouds can be seen sometimes when the conditions are right.
The ionosphere begins within the mesospheric layer at an altitude of about 60km. The ionosphere is not an atmospheric layer but occupies the same space and is a layer of ionised air. In this area and upwards the energy from the sun is so strong that it forces apart molecules and atoms leaving ions and free floating electrons. The ionosphere continues up through the upper atmosphere to heights of about 600km.
The mesopause is the boundary between the mesosphere and the layer above where temperature remains constant with height until it changes on the other side.Pressure reduces with height and in the mesosphere pressure reaches zero and continues to decrease.
Thermosphere
This is the layer above the mesopause and has a strong increase in temperature with height. Molecules are heated by the sun to temperatures up to 1727 degrees Celsius/ 2000 degrees Kelvin. The total air temperature is not high though, this is because air temp is measured by its kinetic energy and the air here is very thin with few particles so the stored energy is not noticeable.
The ionosphere extends through the thermosphere and out into the exosphere.
Exosphere
This is the upper most layer of atmosphere and extends to approximately 10,000km above the earths surface. At this point the atmosphere merges into space and molecules can be lost out of the atmosphere. This area is composed of hydrogen and helium at extremely low densities and is where most satellites will orbit the earth.
Global Radiation Budget
The global radiation budget is the balance between energy from the sun coming in and out of the earth’s atmosphere and its surface. The energy input and output are equal, if they were not the earth would either heat up or cool down, the balance and energy transfer means that the earth has a constant temperature. Once the solar energy enters the atmosphere it does a range of things before leaving, the things it does fuel nearly all life on the planet.
Energy In
Energy from the sun travels 93 million miles in just 8 minutes (speed of light) to reach the earth; once it enters the atmosphere it can be absorbed or reflected. Reflected energy returns to space, while absorbed energy becomes trapped in the earth’s cycles, transferring and changing form before leaving the earth’s atmosphere.
Some energy is reflected straight back into space, firstly in the atmosphere, then by clouds and finally by the surface of the earth (land and oceans). The lighter in colour the higher the amount of energy reflected, hence clouds reflecting more light than anything else. This reflected energy does not interact with the particles and so does not have any warming effects.
Of all the solar energy that enters the atmosphere, 30% is reflected back out.
- Atmosphere 6%
- Clouds 20%
- Land/Oceans 4%
Certain particles in the atmosphere absorb solar radiation, these are mainly, water vapour, dust and carbon dioxide, and the water molecules in clouds also absorb radiation. Land and oceans absorb visible light energy. Different surfaces will absorb solar energy at different rates.
- Atmosphere 16%
- Clouds 3%
- Land/Oceans 51%
Energy Out
All energy that is absorbed must eventually be released and will leave the earth’s atmosphere.
Radiation absorbed by water can be released as latent heat; this means that the water molecule holding the absorbed energy is moved into the atmosphere by the process of evaporation. With latent heat no temperature change is detected.
Sensible heat can be detected as a change in temperature and is an energy transfer; the heated water molecules release the energy back into the atmosphere.
The energy absorbed by the earth and oceans transfer this energy into infra red energy (heat), on sunnier days when higher levels of solar radiation are absorbed by the earths surface you can feel the heat emitting, darker surfaces absorb more radiation and so give off more heat. Some of the energy that is released is then absorbed by the atmosphere.
Energy absorbed by the atmosphere and clouds eventually has to be released and radiates out into space.
- Atmosphere 38%
- Clouds 26%
- Land/Oceans 21% (of which 15% is re-absorbed by atmosphere)
- Latent heat 23%
- Sensible heat 7%
Reference:
www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html
http://vortex.plymouth.edu/atmosphere
www.ace.mmu.ac.uk
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